Somtimes there is no shaping or slant to the shoulders and it's not uncommon in baby sweaters.

BTW: If the fronts also end with 23 sts for the shoulder, you can leave all the back sts on a holder, and then you can join the 23 on each side of the back to the appropriate front (left or right)with 3 needle bind off. I always look for a way to use the 3 needle bind off since it looks so good and it saves sewing.